Electrical stringed musical instrument



Allg- 10, 1937- G. D. BEAUCHAMP 2,089,171

ELECTRICAL STRINGED MUSICAL INSTRUMENT Filed June 2, 1934 5 Sheets-Sheetl 4. 4,. "ff, "ll//f/l/ Aug. 10, 1937. G. D. BEAUCHAMP ELECTRICALSTRTNGED MuscAL INSTRUMENT 3 Sheets-Sheet 2 Filed June 2, 1934 Aug. 10,1937. G. D. BEAUCHAMP ELECTRICAL STRINGED MUSICAL INSTRUMENT ssheets-sheet 5 Filed June 2, 1934 l y l .9.

Patented Aug. 1o, 1937 PATENT OFFICE ELECTRICAL STRINGED MUSICALINSTRUMENT George D. Beauchamp. Los Angeles, lCalif., aslsignor toElectro String Instrument Corporation, Los Angeles; Calif., acorporation of California Application June z, 1934, serial 10,128,711

21 Claims.

This invention relates to musical instruments and it is a general objectof the invention to provide a simple, practical and improved eleclmusical instrument in which the vibrations of the sound producingelements or strings directly vary the reluctance of a magnetic circuitto induce an electric current in a coil within the magnetic neld, whichcurrent is suitably ampliiled l y and transformed into sounds as truereproductions oi.' the sounds produced by the vibrations of the strings.In the present invention the true sound of the vibratory string withallits char.- acteristics is accurately reproduced without the extraneoussounds and vibrations produced by instruments or devices in which amechanical part is made to vibrate through its mechanical associationwith the vibratory string.

Another object of the invention is to provide 2;, an electrical musicalinstrument of the character mentioned including a novel, simplified andparticularly effective electro-magnetic pick-up unit for converting thevibrations of the strings' into an electric current having thecharacteristics of 30 the string vibrations; f

Another object of the invention is to provide an electrical musicalinstrument oi the character mentioned including a singleelectro-magnetic pick-up unit for transforming the vibra- 35 tions ofthe several strings'of the instrument into an electric current. In thedevicex of the present invention the vibrations of each of the severalstrings affect or vary the reluctance oi.' the magnetic circuit of asingle permanent magnet 4o unit to induce an electric current in a coilsuperf imposed on the magnet, and the single unit is not subject to thevariations necessarily inherent in devices involving a plurality ofelectro-magnetic 45 Another object of the invention is to provide anelectrical musical instrument that does not depend upon a sound board,resonance box, or the lilrein the production or propagation of the soundof the`\desired quality, whereby the body of the 50-instrument may be.ofsimple, 'inexpensive construction.

Another .object of the invention is toy provide a musical instrument ofthe character mentioned having tensionedl vibratory strings of different55 diameters and including ajsingle electro-magnetic pick-up unitconstructed and designed to deliver an electric current to an amplifierwhich current is properlyand truly characteristic ci the vibrations oithe several strings.

Another object of the invention is to provide an electrical stringedmusical instrument that is adapted to be played manually in any typicalor desired manner and electrically reproduce the sound or music at aremote point.

Another object of the invention is to provide an electricalmusicalinstrumentvoi the character mentioned that may be easily andconveniently adjusted by the vmusician'orplayer to vary the volume ofthe music or sound produced.

Another object oi the invention is to provide an improvedelectro-magnetic pickup unit'capable of embodiment in stringed musicalinstrume'nts of various characters with little or no modiilcation.

A further object of the invention is to provide an electrical stringedmusical instrument of the character 'mentioned that is small and compactOther objects and features of the invention will be better and morefully understood from the following detailed description of typicalforms and applications of the invention, throughout which descriptionreference may be had to the accompanying drawings, in which:

Fig. 1 is/ a top or plan view of one typical embodiment of the presentinvention. Fig. 2 is an enlarged, transverse, detailed sectional view ofthe pickupr unit and body taken as indicated by line 2-2 on Fig. 1. Fig.3 is an enlarge'd plan elevation of the main portion of the body withthe magnets in cross-section, being a view taken as indicated by line3--3 on Fig. 2.` Fig. 4 is a transverse detailed sectional view taken asindicated by Vline 4-4 on Fig. 3. Fig. 51s an en larged fragmentary`detailed sectional view taken as indicated by line 5-5 on Fig. 1. afragmentary detailed sectional view of the body showing the socket andillustrating the plug in position to enter the socket. Fig. 7 is aWiring diagram of the circuit involved in the present invention. Fig. 3yis an elevation view of the present invention embodied in a. stringedmusical instrument having a wooden body. Fig. 9 is a diagrammatic viewillustrating the non-uniform magnetic iields of the pick up unit andFig. l0 is an enlarged fragmentary diagrammatic View illustrating a.portion of one pole portion Fig. 6 is of the magnet and a portion of onecore membert 'I'he instrument provided by the present inventionincludes, generally, a. body I Il, a plurality of sound propagatingelements or tensloned strings II on the body I0, an electric magneticpickup unit I2 on the body I0 for transforming vibrations of the stringsIl into an induced electric current, and an amplifying unit or system I3for amplifying the` pulsations in said current and converting them intosounds which are the 10 true sounds of the strings II.

The body Il) may be varied considerably in size. shape and construction,and may be constructed of various materials without departing from thespirit of the invention. In the lparticular form l of the invention inFigs. 1 to 7, inclusive, of the drawings, the body III is a simpleintegral casting of metal, such as aluminum or the like, and comprises amajor or main portion I4 and a neck I5. The main portion Il of the bodyis sub- 20 stantially disc shaped, having flat upper and lower sides anda curved or cylindrical periphery.

The neck I5 projects radially with respect to the center of the portionI4 and is of gradually diminishing cross-section. The neck I5 has a withspaced frets I1. The-underside of the neck I5 may be convex or roundedas illustrated in Fig. 4. The body II) may be hollow-as shown in thedrawings to be light in weight, it being uni derstood that in someinstances it may be desirable to make the body I0 solid.`

The strings II are the sound vibration producing elements of theinstrument and are adapted lto be manually plucked or otherwisemanipulated to produce the desired vibrations. The strings Il extenddiametrically across the top oi' the body portion Il and over thefingerboard IB to the outer end of the neck. In theparticular instrumentillustrated there are six spaced strings Il in a substantially parallelseries. The plurality of strings II preferably lie in the same plane,that is, their central longitudinal axes are in or adjacent a commonplane. 'I'he strings II pass over a bridge I8 on the main portion Il ofthe body and over a similar bridge I9 on the outer portion of the neckI5. The inner ends of the strings are suitable secured in openings 20adjacent the bridge I8 and the strings have their outer ends engaged bysecuring and tensioning keys 2I. The portions of the strings IIextending between the bridges I8 and I! are under various degrees oftensile strain and are free to vibrate in the production of recognizedmusical tones. It is to be noted that the oppo- 55 site ends of thestrings I I are rigidly and un yleldingly connected to the rigidmetallicbody Il so that their major portions may have long periods ofvibration with no dampening action due to the absorption of thevibrations by wooden 60 body parts or the like at the ends of thestrings.

In accordance with the usual practice in instruments of the classillustrated the strings II are graduated in diameter. The strings II areformed wholly or in part of conducting material 65 or magnetic materialhaving a different degree of magneticpermeability than the surroundingair to properly influence or an'ect the reluctance of the magnetic fieldin the unit I2.

,The pick-up unit I2 is a magnetic or electro- 70 magnetic device forconverting the actual tone producing vibrations of the strings II intoan induced electric current. The frequencies and the othercharacteristics'of the vibrations of the strings II which maybe termedthe physical 75 properties or the sound produced by the strings fiatupper side forming a fingerboard IB providedA are represented in theelectrical circuit in a proportional or deiinite manner with relation tothe actual physical vibrations of the strings so that the amplifyingunit I3 is actuated by or influenced by the physical properties of thesound to faithfully and accurately reproduce' the sound. The pick-upunit I2 comprises a magnet which, in practice, may be a of like opposedpermanent magnets 22. The magnets are U-shaped or of horse-shoe designand are attached to a supporting plate 23. T'he opposed lower or innerarms A of the magnets 22 have their lower sides resting on the plate 23and the arms A are attached to the plate by suitable screws 24. Inaccordance with the invention the ends of the magnets 22 are in opposedrelation with their poles north to north and south to south,y asindicated in the drawings. This provides a continuous polarity at theopposite sides of the magnet or magnet unit. In the preferredconstruction the confronting or opposed ends of the magnets 22 are inspaced relation.

An opening 25 is provided in the top or upper side of the body portionIl to receive the pickup unit I2. The plate 23 carrying the magnets 22is inserted in the opening 25 and studs or bolts 26 project upwardlyfrom the opposite ends of the plate to extend through openings in plates21 on the body. The plates 21 may carry sleeves 28 for receiving thebolts 2i. It is preferred to mountor support the unit I2 so that it maybe adjusted and accurately set with relation to the strings II. Nuts 29are threaded on the outer ends of the bolts 26 and bear against theouter sides of the plates 21. The nuts 25 may be tightened down toadjust or shift the unit l2 outwardly. Springs III surround the bolts 2Eand are arranged under compression between the plate 23 and the plates21 to normally urge the unit inwardly and hold it against movement.

With the unit I2 mounted or supported as-just described the pair -ofopposed -magnets 22 are disposed transversely of the series of stringsII and their upper or outer arms B are spaced above the top surface ofthe body.' The strings Il pass under the magnet arms B with considerableclearance. A'The strings Il pass through the magnetic field of themagnets 22. The outer arms B of the magnets may be slightly inclinedtoward their opposing ends to compensate for the widened magnetic fieldat their poles or ends. The above described inclination of the magneticarms B is such that the spaces between the arms and strings varysubstantially-in proportion to the intensity of the magnetism of saidarms. l

The pickup unit I2 includes a coil C arranged on or superimposed on thepermanent magnet. The coil C is supported on the inner arms A of thepair of magnets 22 and is to receive an induced, electric current whenthe reluctance of Y the field of the magnet or magnet unit is varied.

The coil C includes a coil form or spool 3i having spaced upper andlower flanges 32. A winding 33 of suitable enameled wire is provided onthe spool )I between the flanges 32. The spool 3| is formed of asuitable insulating material. The number of turns In the winding 23 andthe gauge of the wire of the coil depends upon the particular amplifyingunit I3 with which the instrument is to be used. In accordance with theinvention the coil C is positioned between the north and south poles ofthe magnet and is related to the strings II. to be influenced oraffected by their vibration in the' magnetic field.

' make the members 35 in the form of posts or pins as illustratedthroughout the drawings. The lower ends of the pins rest on or engagethe lower arms A of the magnetswhile the upper ends of the pins projectfrom the spool 3I. 'I'he upper ends of the core pins 35 are spaceddirectly below the strings II as clearly illustrated in Figs. 2 and 3 ofthe drawings. In order to properly compensate for differences in theextent or degree of variation of the magnetic reluctance in the spacesbetween the outer ends of the members 35 and the adjacent arms of themagnet due to the differences in the diameter of the strings II, thespaces between the upper ends of the -pins 35 and the strings II aregraduated substantially in proportion to the graduation in the diameterof the strings.

To eliminate the necessity of aground lead from the coil C one or bothof the end pins 35 project from the surface of the spool 3I and arevengaged by the inner windings 33 which have the enamel removedtherefrom to electrically contact or connect with the pins. -The pins 35thus electrically connected with the inner winding or windings of thecoil Care grounded to the body I0 through the magnet arms A, the plate23, bolts 25 and plates 21. By thus grounding the coil winding to thebody through the magnets the sounds or noises that are characteristics of the coil and magnets are eliminated or avoided. It,

is believed that it will be apparent how the nuts v29 may be employed toset or position the unit where the pins 35 are related to the strings IIto provide for the desired operation of the pickup unit I2. The pins 35in extendinginto the coil C operate to concentrate the magnetic force.in spaced zones or fields in the spaces between their outer ends and theadjacent arms of the magnet and carry the magnetic force into the centerof `the field of the coil. The strings passing be- The particularamplifying unit I3 illustrated in.

the drawings is a one stage audiofrequency amplifying circuit and ismerely typical of the various amplifying systems that may be employed.Means is provided for conveniently connecting the coil C with theamplifying unit I3. In the form-of the invention being described asocket or jack 40 is provided in the body III and is electricallyconnected with the coil C by a conductor Il. The socket 40 'is adaptedto removably receive a plug on the end of a flexible two-conductor cord42 extending from the amplifying unit I3. Means is interposed betweenthe coil C and the amplifying unit I3 for varying the amplification cisound.. The volume control is preferably provided on the instrumentproper to be conveniently accessible to the player. In the drawings Ihave shown a typicalvariabieresistance element 43 connected between thesocket 40 and the coil C and including a control or regulating knob I4projecting from the upper I surface of the body.

Fig. 8 of the drawings illustrates the invention embodied 'in aninstrument in the form of a guitar having a wooden body III". The bodyIIIIa has the usual resonance -box I4* and the neck I5. The strings IIaextend across the upper surface of the body and are maintained under therequired tension by keys 2li. The electromagnetic pickup unit I2 issupported on the body Ita so that the strings Il" pass under its outer`magnet arms A1.

'I'he strings II*i pass between the magnet arms A1 andthe coil of theunit.

The unit I2a operates in the same manner as the v unit I2 and suitableconductors extend from the 'board I6 by the fingers of the player or bya steel or playing ybar held in the -players hand.

Asbest illustrated in Figs. 9 and 10 of the drawings. the magnetic fluxpasses between the upper or outer arms of the magnets 22 and the members35 in concentrated non-uniform fields F. That is, the lines of magneticforce asv illustrated diagrammatically by the spaced lines L in Figs. 9and 10 are relatively concentrated in the spaces or fields F between theouter arms of `the magnets and the exposedends of the pole members 35and converge td or iiare outwardly from trie relatively limited surfacespresented by ends of the members 35. ing in Figs. 9 and 10 are notintended to illustrate the total lines of 'magnetic force in the fieldsF and merely illustrate the general grouping and the general directionof the lines of force in the fields when the strings Il are in theirnormal positions. The vibratory strings II of magnetic material passthrough these concentrated non-uniform elds F and when they arestationary or unmoved there is a fixed or stable condition of magneticflux and reluctance in the fields F. Movement or vibration of a string II in any direction alters this fixed condition of the field F throughWhch it passes varying the reluctance in the space or field F. 'Ihevariation in the reluctance of the field F induces a current in the coilC. The current induced in the coil C has characteristics proportional tothe characteristics of the movement of the strings II. As the fields Fare non-uniform or composed of fiaring or converging lines L' ofmagnetic force, movement-or vibration of the strings II in thedirectionof the longitudinal axes of the members 35 and movement of thestrings II in a direction transverse of said axes both vary thereluctances of the fields F and thus induce a currentin the coil.However, lthe tone or the character of the tone produced by theamplifier I3 resulting from the current induced in the coil C byvariation in the reluctance of a given field F caused by movement orvibration of the string II therein inv a direction substantiallytransverse ofthe longitudinal axis of the The lines L appcaradjacentmember 85 is different from that resulting from vibration of the stringin a direction substantially axially of said axis. Assuming that astring Ii is vibrated to move substantially 5 transversely through itseld F relative tothe general direction of the lines of force L, themagnetic path through the string il is longervor greater when the stringis in the end positions oi its vibratory motion than when the string isl in the intermediate position of such' motion. The reluctance ofthespace or field F therefore is greaterwith the string Il'kin the endpositions ofits vibratory motion" than with the string in theintermediate position of its movement. 'Ihus l vibration of the stringIlhorlzontally or substantially transverse of the longitudinal axis ofthe member l induces a current in the coil VC which isconverted by theamplifier Il into a tone in which the second harmonic of the note ofthestring predominates. Assuming that the above-mentioned string Il isvibrated in a general vertical direction or in a direction substantiallyparallel with or axially of the longitudinal u axis of the member 35,the effect of the string in reducing the reluctance of the ileld F isgreater when at the end of its vibratory travel nearest the member l5than when at the end of its travel nearest the arm oi the,` magnet 22.This is due to this 'particular movement of the string Il in thenon-uniform -or substantially fan shaped field F made up of the lines Lof force converging. to or flaring from the end of the member 35.Vibration of the string II in a substantially vertical direction or in adirection substantially axial of the member II induces a current in thecoil C whichact'uates the amplliler to produce a tone which is stronglythat of the fundamental .note of the string. While it may not bepractical to vibrate the strings Il in truly vertical or truly40'horiaontaldirections thev player or musician may at will readily varyand control the character of the tones produced electrically by theinstrument.

by pluclring or otherwise vibrating the strings Il to vibrate in agenerally vertical direction or a generally horizontal direction. Thesoundproduced by the'system or unit I3 therefore has all the tonalqualities of the sound which results from the physical vibration of thestrings il. 'I'he element `Il may be employed to control or varythevolume of the sound produced by the uniti) and ls convenientlyaccessible to the hand of the player or musician employed to pluck orvibrate the strings. The sound is reproduced without the mechanicalvibration of any part at the pickup unit l2 yother than the 'strings Ii.The resultant music or sound accordingly does not have any extraneousvibrations or unwanted p qualities.

Having described only typical preferred forms a0 and applications ofA myinvention I do not wish to be limited or restricted to the speciiicforms and applications herein set forth, but wish to reserve to myselfany modiilcations or variations that may appear to those skilled in theart or fall within the scope of 4vthe following claims.

Having described my invention, I claim:

l; A pick up unit 'for use with the vibratory strings of a musicalinstrument, including a permanent magnet, a coil supported by the magnetbetween its poles, means mounting themagnet to have thestrings passbetween one of its' poles and the coil, and core members within the coileach having anend facing a string.l

2. In combination, a series of tensioned strings of' magnetic materialof different diameters, a

' single magnet having its pole portions at opposite sides of the seriesof strings, a coil between the pole portions of the magnet, andAmagnetic core members extending from one of the pole Portions toward theother and terminating to form string ,spaces which vary in size with,thestrings.

l 3. In combination, a plurality of spaced vibratory strings of magneticmaterial, and a pick up unit including, a pair, of permanent magnetsarranged to surround the strings with their corresponding poles opposed,a coil within the field of the magnets, and means supporting the magnetsand coil for adjustment yrelative to the strings.

'4. A musical instrument comprising, a body to be held by the player, aplurality of spaced vibratory strings of magnetic material at theexterior of the body having portions accessible to be engaged by theplayer, a permanent magnet having a polar part extending over thestrings to cover the same adjacent said portions and form a guardtherefor and a rest for the operator, and

a coil within the ileld of the magnet sensitive to disturbances therein.

5. A musical instrument comprising, a body to be held by the player, aplurality of spaced vibratory strings of magnet material at theexterior4 of the body having portions accessible to be engaged by theplayer, a. permanent magnet having its polar parts spaced above andbelow the lstrings whereby the strings pass through a dense portion ofthe field of the magnet, the upper polar parts extending over thestrings adjacent said portions to cover the same and form a guard i'orthe strings and a hand rest for'the player, and a coil insaid fieldsensitive to disturbances therein.

6. A musical instrument comprising, a pluralment, said pick up unitcomprising, an elongate magnet unit disposed transversely of the stringsto have a polar part above the strings, a coil carried by the magnet toreceive an inducedl current from its field, and means for shifting themagnet from eitherend to move it relative t0 the strings to tune thepick up unit.

8. A" pick up unit for use in combination with the vibratory string ofan instrument including, a magnet having spaced polar parts, an induc- Ition coil positioned between the said polar parts,

and means ior supporting the magnet and coil so that the string passesthrough the space' between the coil and one of said parts wherebyvibration of the string varies the reluctance of the said space toinduce a current in the coil.`

9. A pick up means for use in combination with a musical instrumenthavinga vibratory string of. magnetic material,said pick up meansincluding, a magnet having spaced polar parts, a coil positioned betweenthe said parts, the magnet and coil being positioned so that the stringvpasses through the space between the coil and one of said parts wherebyvibration oi' the string varies the reluctance of a relatively denseportion of the magnetic ileld to induce a current in the coil,

and means carrying the magnet and coil for adjustment relative to thestring.

10. In combination, a series of vibratory strings of magnetic materialof different diameters, a magnet,a coil in the field of the magnet, themagnet being positioned so that the strings pass through its field,magnetic core members extending from one pole portion of the magnet andpassing through the coil toward the other pole portion of the magnet andterminating at points spaced from the said other pole portion to leavespaces through which the strings pass, and means for shifting the magnetto vary the relation between the strings and said spaces.

11. A musical instrument comprising a body to be held by the player, aplurality of vibratory strings of magnetic material extending across anexterior face of the body in spaced relation thereto, a permanent magneton the body havinga polar part related to the strings to cover thestrings and form a guard therefor and a hand rest for the player, and acoil in the field of the magnet sensitive to disturbances therein.

12. In a musical instrument, a series of spaced vibratory strings ofmagnetic material, an cion-- gate magnet unit disposed. transversely ofthe strings where the strings pass through its field, a coil carried bythe magnet unit to receive an induced current from the magneticeld, andmeans for shifting the magnet from either end to adjust it relative tothe strings.

13. In a musical instrument, a series of spaced Vibratory strings ofmagnetic material, an elongate magnet unit disposed transversely of thestrings where the strings pass through its field, a coil in the magneticfield of the unit to receive an induced current therefrom, and means forrocking the magnet unit in a plane substantially transverse of thestrings to adjust it relative to the strings. V

14. In a musical instrument, a series of spaced vibratory strings ofmagnetic material, an elongate magnet unit disposed transversely of thestrings where the strings pass through its field, a coil in the magneticfield of the unit to receive an induced current therefrom, and means fortilting the magnet unit in a plane substantially' transverse of thestrings, said means including supportsfor the magnet unit at points atopposite sides of the series of strings.

15. In combination, a vibratory string of magnetic material, a magnethaving pole portions at opposite sides of the string, a coil between thepole portions of the magnet, a .magnetic core member extending from oneof the pole portions toward the other pole vportion and terminating at apoint spaced therefrom to forma space' through which the string passes,and means for shifting the magnet to vary the positions of the coremember and the said other pole portion with relation to the string.

16. A musical instrument comprising a body, a

plurality of exposed vibratory strings extending across a face of thebody in' spaced relation thereto, a pair of opposed magnets on the bodyhaving polar portions disposed transversely of the strings and relatedto the strings to form a guard therefor, said guard extending over thestrings to cover the same, and a coil in the field of the pair ofmagnets sensitive to disturbances therein.

17. In a pick up unit, vibratory strings of magnetic material, a magnethaving spaced pole portions and positioned so that the strings passbetween said pole portions, a plurality of magnetic pole members on oneof said pole portions, each member having a limited surface of magneticattraction adjacent one string whereby the strings act in zones whereinthe lines of magnetic force flare inwardly to said limited surfaceavandVa coil surrounding the pole members.

18. In a pick up u nit, vibratory strings of magnetic material, a singlepermanent magnet having a series of projecting pole parts of likepolarity, each pole part presenting a limited surface adjacent a stringwhereby the lines of magnetic force flare outwardly from said surfacesabout the strings, and an induction coil surrounding said series ofparts.

19. In a pick up unit, a plurality of vibratory strings of magneticmaterial, a magnet having spacedpole portions positioned so that thestrings pass between the pole portions in closer proximity to one thanthe other, magnetic posts extending from said other ,pole portion andeach having a surface of limited extent adjacent a string and opposingthe first mentioned pole portion whereby the strings vibrate in a zonewhere the lines of magnetic force converge to said surfaces, and a coilin the field of the magnet.

20. In a pick up unit, a plurality of vibratory strings o'f magneticmaterial having their axes in a common plane, amagnet having a poleportion adjacent the strings and` inclined with respect to said plane sothat the spaces between said portion and the strings vary substantiallyin proportion to the intensity of the magnetism of said pole portion,and a coil in the field of the magnet.

21. In a pick up unit, a plurality of vibratory strings of magneticmaterial having their axes in a common-plane, a magnet having a poleportion adjacent the strings and inclined with respect lto said plane sothat the spaces between said

